Question

phase change diagram
temperature (°c)
energy
what is happening to the energy...
from liquid to solid?
from solid to liquid?
from liquid to gas?
from gas to liquid?

Explanation:

Step1: Analyze liquid - to - solid phase

When a substance changes from liquid to solid (freezing), it releases energy. This is an exothermic process as the molecules slow down and arrange into a more ordered solid structure.

Step2: Analyze solid - to - liquid phase

When a substance changes from solid to liquid (melting), it absorbs energy. The added energy is used to break the intermolecular forces holding the solid - state structure together.

Step3: Analyze liquid - to - gas phase

When a substance changes from liquid to gas (vaporization), it absorbs energy. The energy is required to separate the molecules from the relatively close - packed liquid state to the more spread - out gas state.

Step4: Analyze gas - to - liquid phase

When a substance changes from gas to liquid (condensation), it releases energy. The molecules in the gas phase lose energy and come closer together to form a liquid.

Answer:

From liquid to solid: Energy is released.
From solid to liquid: Energy is absorbed.
From liquid to gas: Energy is absorbed.
From gas to liquid: Energy is released.